Trends and abrupt detection of temperature and precipitation extremes are important in climate change research. Based on the meteorological data from 68 stations in the arid region of Northwest China (ARNC), we analyzed the trend and abrupt change in temperature and precipitation extremes from 1961 to 2010. Results showed that abrupt change in both temperature and precipitation extremes in Northwest China occurred in around 1986. Interestingly, an abrupt change in Index B of the Tibetan Plateau (TPI_B) was detected in 1985. The temperature and precipitation extremes had strong and significant associations with TPI_B over the period of 1961–2010 (R = 0.685, p < 0.01, and R = 0.441, p < 0.01, respectively). They behaved consistently, with a weakening and decreasing trend from 1961 to 1984 and a strengthening and increasing trend from 1985 to 2010. Thus, TPI_B was probably an important factor in the abrupt change in both temperature and precipitation extremes in the ARNC.